1. Field of the Invention
The invention relates to a phase change memory device and method for fabricating the same, and more particularly to a phase change memory device with a relatively higher device density and a method for fabricating the same.
2. Description of the Related Art
A phase change memory (PCM) device may potentially serve as a 64-megabyte (MB) or greater stand-alone non-volatile memory, such as a flash memory. A PCM device stores data by changing the state of a phase change material from an amorphous state to crystalline state using a heating electrode. Before PCM devices become a mainstream replacement for flash memory, however, they must first achieve excellent electrical and thermal performance. Fabrication of non-volatile memory with relatively higher device density using conventional fabrication processes is, thus, a major aim of researchers.
U.S. Pat. No. 6,501,111 issued by Intel Corporation discloses a conventional three-dimensional PCM (3D-PCM) 212 with a cup-shaped bottom electrode 206 as shown in FIG. 1a. A contact area between a phase change material 207 and a bottom electrode can serve as a contact area between the phase change material 207 and a width of the cup-shaped bottom electrode 206, thus, device density is improved. However, a bottleneck occurs when minimizing the device area using conventional fabrication processes, thus, making the invention unsuitable for photolithography processes with critical dimensions (CD) below 0.1 μm. As shown in FIG. 1b, EP Pat. No. 1339111 issued by ST Microelectronics (STM) Corporation discloses a PCM formed by filling a phase change material into a contact hole 57 with a nano-level CD or a minitrench 58 to reduce the contact area 58 between the phase change material and a cup-shaped heating electrode 22, thus, achieving higher device density. However, if the CD of the contact hole is too small to be filled with phase change material, a seam problem occurs.
A PCM device with higher device density is desirable.